The terms "sex" and "gender" are often used interchangeably within the general community. However, although highly related, sex and gender are distinct concepts. By bringing these two concepts together into a single standard, it is possible to explain the relationship between them and provide context for their appropriate use. In practice, it is expected that most users will need to collect only one of sex or gender to meet their statistical needs.

The sex and gender standard includes guidelines on the collection of counts of persons who do not fall within the male or female categories of sex and/or gender. Consequently the standard's data collection procedures recognise the need to include a third category to ensure the standard caters for the whole population.